Hepatitis C virus (HCV) infection has a worldwide prevalence of 3% and is the main entity responsible for liver transplantation in developed countries for treatment of cirrhosis. In the United States, HCV is the most common chronic blood borne infection affecting 1.8% of the population and appears to be the major etiologic factor responsible for the recent doubling of HCC in the United States. Current therapy consists of pegylated interferon-1 (PEG-IFN) and ribavirin (RBV). 70% of patients in the United States are infected with genotype 1 for which sustained virologic response (SVR) is only 42-46%. Generally, therapy of all genotypes can be accompanied by adverse effects and contraindications to therapy are not infrequent. For these reasons there is the need to develop additional therapies that are less toxic and result in higher SVR either as adjuncts or replacement therapies. We have identified the heat shock proteins (HSP)s HSP40 and HSP70 in complex with the HCV encoded protein NS5A through mass spectrometric analysis. We confirmed an NS5A/HSP interaction by confocal microscopy and coimmunoprecipitation. HSP40 and HSP70 knockdown both reduced infectious viral particle production in a HCV cell culture system. Treatment with the heat shock protein synthesis inhibitors Quercetin and KNK437 reduced infectious particle production at non-toxic concentrations. This striking inhibition of virus production combined with its known low toxicity and use in previous and ongoing clinical trials serves to motivate this bench to bedside proposal to study treat HCV infected patients with Quercetin. In this proposal, our goals are to further understand the impact of HSP40 and HSP70 and heat shock protein synthesis inhibitors on HCV infection and determine Quercetin's safety and antiviral activity in patients suffering from chronic HCV infection in a phase I clinical trial. To achieve this we propose three interrelated specific aims: 1. We will determine the importance of heat shock proteins 40 and 70 in hepatitis C virus production in the HCVcc model. 2. We will determine the impact of heat shock protein synthesis inhibitors on hepatitis C viral infection in the HCVcc model. We will test the clinical feasibility of the heat shock protein synthesis inhibitor Quercetin on patients with chronic hepatitis C viral infection through a phase I trial. Further understanding of heat shock proteins and heat shock protein synthesis inhibition in HCV infection may allow for successful treatment of chronic hepatitis C and reduce the incidence of cirrhosis and hepatocellular carcinoma.